1. Field of the Invention
The present invention relates to a display device which includes a memory type display constituted of a display layer capable of displaying an image by displaying predetermined colors according to an applied voltage and a pair of electrodes disposed so as to sandwich the display layer, and a driving circuit capable of applying a predetermined voltage between the pair of electrodes so that a predetermined image is displayed on the display layer, and to an image erasing method suitable for the display device.
2. Description of the Related Art
Heretofore, as a display device of this type, there has been known, for example, one disclosed in JP2002-357853A, which includes: an electrophoretic display constituted of a display layer having disposed therein multiple microcapsules containing electrophoresis dispersion liquid formed of black charged particles and a white dispersion medium, and a pair of electrodes (transparent electrode and non-transparent electrode) disposed so as to sandwich the display layer; and a driving circuit capable of applying any given voltage between the transparent electrode and non-transparent electrode.
In such a display device, generally, a voltage is applied between the transparent electrode and non-transparent electrode to cause the charged particles of any given microcapsule sandwiched therebetween to be adsorbed to the transparent electrode side so that some information is displayed on the transparent electrode side with the adsorbed charged particles.
Also, when the driving circuit is changed from the state in which the charged particles are adsorbed to the transparent electrode side to the OFF state (release state), the electric charges are retained on both of the electrodes. Thus, the former state is sustained by the Coulomb force of the retained charges. Specifically, with no electrical power applied, the state in which the charged particles are adsorbed is sustained, whereby the information is kept to be displayed on the transparent electrode side.
However, in the conventional display device described above, the information displayed on the transparent electrode side remains displayed until any operation of intentionally erasing the information is performed. Thus, for example, when the driving circuit fails to operate due to a trouble of the display device, the displayed information cannot be erased. In this case, the displayed information may be seen by others.
Especially, when the driving circuit fails to operate during the display of the kind of information which is not permitted to be shown to others, the display device cannot be sent for repair, and cannot be scrapped, either. Consequently, the display layer must be destroyed to prevent the displayed information from being seen by others, thus costing much time and money.
To solve the above unsolved problem of the conventional display devices, an object of the present invention is to provide a display device in which the displayed information can be erased even when the device is in a failed state, and an image erasing method suitable for the display device.